全文获取类型
收费全文 | 3041篇 |
免费 | 68篇 |
国内免费 | 3篇 |
专业分类
电工技术 | 38篇 |
综合类 | 3篇 |
化学工业 | 636篇 |
金属工艺 | 34篇 |
机械仪表 | 37篇 |
建筑科学 | 199篇 |
矿业工程 | 21篇 |
能源动力 | 62篇 |
轻工业 | 160篇 |
水利工程 | 27篇 |
石油天然气 | 49篇 |
无线电 | 170篇 |
一般工业技术 | 385篇 |
冶金工业 | 844篇 |
原子能技术 | 20篇 |
自动化技术 | 427篇 |
出版年
2022年 | 27篇 |
2021年 | 36篇 |
2019年 | 34篇 |
2018年 | 36篇 |
2017年 | 54篇 |
2016年 | 48篇 |
2015年 | 42篇 |
2014年 | 42篇 |
2013年 | 180篇 |
2012年 | 71篇 |
2011年 | 106篇 |
2010年 | 84篇 |
2009年 | 94篇 |
2008年 | 106篇 |
2007年 | 110篇 |
2006年 | 98篇 |
2005年 | 113篇 |
2004年 | 77篇 |
2003年 | 96篇 |
2002年 | 69篇 |
2001年 | 74篇 |
2000年 | 52篇 |
1999年 | 64篇 |
1998年 | 108篇 |
1997年 | 69篇 |
1996年 | 70篇 |
1995年 | 47篇 |
1994年 | 40篇 |
1993年 | 42篇 |
1992年 | 39篇 |
1991年 | 33篇 |
1990年 | 54篇 |
1989年 | 47篇 |
1988年 | 47篇 |
1987年 | 53篇 |
1986年 | 36篇 |
1985年 | 49篇 |
1984年 | 39篇 |
1983年 | 35篇 |
1982年 | 38篇 |
1981年 | 32篇 |
1980年 | 27篇 |
1979年 | 34篇 |
1978年 | 34篇 |
1977年 | 30篇 |
1976年 | 50篇 |
1975年 | 30篇 |
1974年 | 32篇 |
1973年 | 42篇 |
1972年 | 25篇 |
排序方式: 共有3112条查询结果,搜索用时 15 毫秒
71.
Bingo Wing‐Kuen Ling Charlotte Yuk‐Fan Ho Raymond Shing‐Keung Leung Peter Kwong‐Shun Tam 《International Journal of Circuit Theory and Applications》2004,32(2):57-64
This letter explains the oscillatory behaviours exhibited in a second‐order digital filter with saturation‐type non‐linearity via the Hopf bifurcation theorem. It is shown that depending on the bifurcation parameter, the state variables may converge to zero even when the eigenvalues of the system matrix are outside the unit circle. Copyright © 2004 John Wiley & Sons, Ltd. abstract 相似文献
72.
Meta-analysis was used to aggregate results from studies examining the relationship between intelligence and leadership. One hundred fifty-one independent samples in 96 sources met the criteria for inclusion in the meta-analysis. Results indicated that the corrected correlation between intelligence and leadership is .21 (uncorrected for range restriction) and .27 (corrected for range restriction). Perceptual measures of intelligence showed stronger correlations with leadership than did paper-and-pencil measures of intelligence. Intelligence correlated equally well with objective and perceptual measures of leadership. Additionally, the leader's stress level and the leader's directiveness moderated the intelligence-leadership relationship. Overall, results suggest that the relationship between intelligence and leadership is considerably lower than previously thought. The results also provide meta-analytic support for both implicit leadership theory and cognitive resource theory. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
73.
Min-Cheol Kim Raymond H. W. Lam Todd Thorsen H. Harry Asada 《Microfluidics and nanofluidics》2013,15(3):285-296
For successful cell culture in microfluidic devices, precise control of the microenvironment, including gas transfer between the cells and the surrounding medium, is exceptionally important. The work is motivated by a polydimethylsiloxane (PDMS) microfluidic oxygenator chip for mammalian cell culture suggesting that the speed of the oxygen transfer may vary depending on the thickness of a PDMS membrane or the height of a fluid channel. In this paper, a model is presented to describe the oxygen transfer dynamics in the PDMS microfluidic oxygenator chip for mammalian cell culture. Theoretical studies were carried out to evaluate the oxygen profile within the multilayer device, consisting of a gas reservoir, a PDMS membrane, a fluid channel containing growth media, and a cell culture layer. The corresponding semi-analytical solution was derived to evaluate dissolved oxygen concentration within the heterogeneous materials, and was found to be in good agreement with the numerical solution. In addition, a separate analytical solution was obtained to investigate the oxygen pressure drop (OPD) along the cell layer due to oxygen uptake of cells, with experimental validation of the OPD model carried out using human umbilical vein endothelial cells cultured in a PDMS microfluidic oxygenator. Within the theoretical framework, the effects of several microfluidic oxygenator design parameters were studied, including cell type and critical device dimensions. 相似文献
74.
Scott R Boss Laurie J Kirsch Ingo Angermeier Raymond A Shingler R Wayne Boss 《欧洲信息系统杂志》2009,18(2):151-164
Information security has become increasingly important to organizations. Despite the prevalence of technical security measures, individual employees remain the key link – and frequently the weakest link – in corporate defenses. When individuals choose to disregard security policies and procedures, the organization is at risk. How, then, can organizations motivate their employees to follow security guidelines? Using an organizational control lens, we build a model to explain individual information security precaution-taking behavior. Specific hypotheses are developed and tested using a field survey. We examine elements of control and introduce the concept of ‘mandatoriness,’ which we define as the degree to which individuals perceive that compliance with existing security policies and procedures is compulsory or expected by organizational management. We find that the acts of specifying policies and evaluating behaviors are effective in convincing individuals that security policies are mandatory. The perception of mandatoriness is effective in motivating individuals to take security precautions, thus if individuals believe that management watches, they will comply. 相似文献
75.
Kate Sanders Sally Fincher Dennis Bouvier Gary Lewandowski Briana Morrison Laurie Murphy Marian Petre Brad Richards Josh Tenenberg Lynda Thomas Richard Anderson Ruth Anderson Sue Fitzgerald Alicia Gutschow Susan Haller Raymond Lister Renée McCauley John McTaggart Christine Prasad Terry Scott Dermot Shinners-Kennedy Suzanne Westbrook Carol Zander 《Expert Systems》2005,22(3):121-128
Abstract: This paper presents a case study of the use of a repeated single‐criterion card sort with an unusually large, diverse participant group. The study, whose goal was to elicit novice programmers' knowledge of programming concepts, involved over 20 researchers from four continents and 276 participants drawn from 20 different institutions. In this paper we present the design of the study and the unexpected result that there were few discernible systematic differences in the population. The study was one of the activities of the National Science Foundation funded Bootstrapping Research in Computer Science Education project (2003). 相似文献
76.
Walters Glenn D.; McGrath Robert E.; Knight Raymond A. 《Canadian Metallurgical Quarterly》2010,22(1):149
The taxometric method effectively distinguishes between dimensional (1-class) and taxonic (2-class) latent structure, but there is virtually no information on how it responds to polytomous (3-class) latent structure. A Monte Carlo analysis showed that the mean comparison curve fit index (CCFI; Ruscio, Haslam, & Ruscio, 2006) obtained with 3 taxometric procedures—mean above minus below a cut (MAMBAC), maximum covariance (MAXCOV), and latent mode factor analysis (L-Mode)—accurately identified 1-class (dimensional) and 2-class (taxonic) samples and produced taxonic results when applied to 3-class (polytomous) samples. From these results it is concluded that using the simulated data curve approach and averaging across procedures is an effective way of distinguishing between dimensional (1-class) and categorical (2 or more classes) latent structure. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
77.
Milo Hricovíni Raymond J. Owens Andrzej Bak Violetta Kozik Witold Musia Roberta Pierattelli Magdalna Mjekov Yoel Rodríguez Robert Musio Aneta Slodek Pavel tarha Karina Pitak Dagmara Sota Wioletta Florkiewicz Agnieszka Sobczak-Kupiec Josef Jampílek 《International journal of molecular sciences》2022,23(23)
The knowledge of interactions between different molecules is undoubtedly the driving force of all contemporary biomedical and biological sciences. Chemical biology/biological chemistry has become an important multidisciplinary bridge connecting the perspectives of chemistry and biology to the study of small molecules/peptidomimetics and their interactions in biological systems. Advances in structural biology research, in particular linking atomic structure to molecular properties and cellular context, are essential for the sophisticated design of new medicines that exhibit a high degree of druggability and very importantly, druglikeness. The authors of this contribution are outstanding scientists in the field who provided a brief overview of their work, which is arranged from in silico investigation through the characterization of interactions of compounds with biomolecules to bioactive materials. 相似文献
78.
Alec C. Gleason Ghanashyam Ghadge Yoshifumi Sonobe Raymond P. Roos 《International journal of molecular sciences》2022,23(18)
Ribosome profiling and mass spectroscopy have identified canonical and noncanonical translation initiation codons (TICs) that are upstream of the main translation initiation site and used to translate oncogenic proteins. There have previously been conflicting reports about the patterns of nucleotides that surround noncanonical TICs. Here, we use a Kozak Similarity Score algorithm to find that nearly all of these TICs have flanking nucleotides closely matching the Kozak sequence. Remarkably, the nucleotides flanking alternative noncanonical TICs are frequently closer to the Kozak sequence than the nucleotides flanking TICs used to translate the gene’s main protein. Of note, the 5′ untranslated region (5‘UTR) of cancer-associated genes with an upstream TIC tend to be significantly longer than the same region in genes not associated with cancer. The presence of a longer-than-typical 5′UTR increases the likelihood of ribosome binding to upstream noncanonical TICs, and may be a distinguishing feature of a number of genes overexpressed in cancer. Noncanonical TICs that are located in the 5′UTR, although thought by some to be disadvantageous and suppressed by evolution, may translate oncogenic proteins because of their flanking nucleotides. 相似文献
79.
Elena Piacenza Simona Campora Francesco Carfì Pavia Delia Francesca Chillura Martino Vito Armando Laudicina Rosa Alduina Raymond Joseph Turner Davide Zannoni Alessandro Presentato 《International journal of molecular sciences》2022,23(20)
The intense use of tellurium (Te) in industrial applications, along with the improper disposal of Te-derivatives, is causing their accumulation in the environment, where oxyanion tellurite (TeO32−) is the most soluble, bioavailable, and toxic Te-species. On the other hand, tellurium is a rare metalloid element whose natural supply will end shortly with possible economic and technological effects. Thus, Te-containing waste represents the source from which Te should be recycled and recovered. Among the explored strategies, the microbial TeO32− biotransformation into less toxic Te-species is the most appropriate concerning the circular economy. Actinomycetes are ideal candidates in environmental biotechnology. However, their exploration in TeO32− biotransformation is scarce due to limited knowledge regarding oxyanion microbial processing. Here, this gap was filled by investigating the cell tolerance, adaptation, and response to TeO32− of a Micromonospora strain isolated from a metal(loid)-rich environment. To this aim, an integrated biological, physical-chemical, and statistical approach combining physiological and biochemical assays with confocal or scanning electron (SEM) microscopy and Fourier-transform infrared spectroscopy in attenuated total reflectance mode (ATR-FTIR) was designed. Micromonospora cells exposed to TeO32− under different physiological states revealed a series of striking cell responses, such as cell morphology changes, extracellular polymeric substance production, cell membrane damages and modifications, oxidative stress burst, protein aggregation and phosphorylation, and superoxide dismutase induction. These results highlight this Micromonospora strain as an asset for biotechnological purposes. 相似文献
80.
Dispersion modeling of polycyclic aromatic hydrocarbons from combustion of biomass and fossil fuels and production of coke in Tianjin, China 总被引:2,自引:0,他引:2
Tao S Li X Yang Y Coveney RM Lu X Chen H Shen W 《Environmental science & technology》2006,40(15):4586-4591
A USEPA, procedure, ISCLT3 (Industrial Source Complex Long-Term), was applied to model the spatial distribution of polycyclic aromatic hydrocarbons (PAHs) emitted from various sources including coal, petroleum, natural gas, and biomass into the atmosphere of Tianjin, China. Benzo[a]pyrene equivalent concentrations (BaPeq) were calculated for risk assessment. Model results were provisionally validated for concentrations and profiles based on the observed data at two monitoring stations. The dominant emission sources in the area were domestic coal combustion, coke production, and biomass burning. Mainly because of the difference in the emission heights, the contributions of various sources to the average concentrations at receptors differ from proportions emitted. The shares of domestic coal increased from approximately 43% at the sources to 56% at the receptors, while the contributions of coking industry decreased from approximately 23% at the sources to 7% at the receptors. The spatial distributions of gaseous and particulate PAHs were similar, with higher concentrations occurring within urban districts because of domestic coal combustion. With relatively smaller contributions, the other minor sources had limited influences on the overall spatial distribution. The calculated average BaPeq value in air was 2.54 +/- 2.87 ng/m3 on an annual basis. Although only 2.3% of the area in Tianjin exceeded the national standard of 10 ng/m3, 41% of the entire population lives within this area. 相似文献